module 3 - 7.2 mammalian gaseous exchange system Flashcards
what do all organisms require?
nutrients
the ability to excrete waste
how do many simple organisms exchange substances?
directly across their external surfaces
why do large organisms require specialised gas exchange and transport systems?
to transport substances (oxygen, nutrients) to their cells efficiently
how do fish exchange substances?
across their gills
how do insects exchange substances?
openings on their surfaces called SPIRACLES
where does gas exchange occur in mammals?
lungs and a part of the alveoli
why are all inner exchange surfaces moist?
because O2 (& some CO2) needs to be changes into aqueous solutions and needs O2to get into cells
why do land animals face a constant battle between ventilation, gas exchange, and retaining water?
- gas exchange surfaces are moist to aid diffusion by oxygen dissolving in water
- ventilation causes this water to readily evaporate
what is breathing? (in terms of ventilation)
ventilation of the lungs
how are the lungs and ribcage stuck together?
outside surface of lungs stuck to inside membrane of ribcage
what is the pleural membrane?
the double membrane that the lungs are enclosed in
what is the pleural cavity?
the space between 2 membranes and is filled with small amount of pleural fluid
what does the pleural fluid do?
- lubricates the lungs
- adheres to outer walls of the lungs to thoracic cavity by water cohesion
how is the pleural fluid connected to the membrane
hydrogen bonding
what are three important functions of the nasal cavity?
- large SA and good blood supply
- hairy lining
- moist surfaces
why is a large SA and good blood supply, an important functions of the nasal cavity?
warms the air as it passes into the body
how is hairy lining an important function of the nasal cavity?
hairs trap dust & bacteria in mucus & prevent them from reaching lungs causing infection
how is moist surfaces an important function of the nasal cavity?
increases humidity of incoming air, reduces evaporation of water in lungs
what is the structure of trachea?
- supported by layer of cartilage that holds trachea open and prevents collapse
- rings are incomplete - allows it to bend when food swallowed down oesophagus
- lined with ciliated epithelial & goblet cells that prevent dust & bacteria
what do goblet cells do?
secrete mucus made of mucin, keeps airways clear
what do the ciliated epithelial cells do?
beat regularly to move micro organisms and dust particles along the mucus
what are the bronchus?
- bronchus are extensions of trachea - split in 2 for left and right lung
- very similar structure to trachea but smaller
- cartilage rings hold pipe open
what are the brochioles?
- bronchus split into smaller bronchioles
- no cartilage and held open by smooth muscle
- when muscle contracts, bronchioles contract (dependent on air flow)
- lined with thin layer of epithelial tissues
what is the alveoli?
- little air sacs, most gas exchange occurs
- made of thin layer of flattened epithelial cells, and some collagen and elastic fibres
- the elastic fibres cause recoil - helps move air out of alveoli
what are 4 features of efficient gas exchange?
- large SA
- thin layers
- constant blood supply
- ventilation
how is a large SA a feature of efficient gas exchange?
large area for exchange of materials to occur
how is thin layers a feature of efficient gas exchange?
creates a short diffusion path for gases, increases speed of exchange
how is good, constant blood supply a feature of efficient gas exchange?
- maintains large diffusion gradient
- ensures exchanged substances are constantly moving
how is ventilation a feature of efficient gas exchange?
maintains the diffusion gradient, faster & more efficient
what happens to the chest volume during inhalation?
chest cavity increases in volume, lowering pressure in the lungs
what does the decrease in pressure during inhalation lead to?
- leads to a tendency for the lungs to collapse
- alveoli lacks support from cartilage
what is a lung surfactant?
a phospholipid that coats surfaces of the lungs
what happens without the lung surfactant?
watery lining of alveoli creates surface tension, causing them to collapse
why do animals need to maintain a concentration gradient across their exchange surfaces?
- so oxygen will diffuse into the blood and carbon dioxide will diffuse out
- maintained by ventilation
how do fish manage to maintain a concentration gradient across exchange surfaces?
keeping a continuous stream of oxygenated water moving over their gills
how does ventilation occur?
pressure changes in the thoracic cavity
what does the rib cage provide?
a cage where pressure changes to facilitate breathing
what is inspiration?
- breathing in
- causes lungs to move up and out
what active processes are caused when inspiring?
diaphragm - moves down
intercostal muscles - moved the ribs up and out
thoracic volume - increases
thoracic pressure - decreases
air flow - INTO the lungs
what does air flow in to/ out of the lungs during inspiration/ expiration ?
to equalise pressure difference
what passive processes are caused by expiration?
diaphragm - moves up
intercostal muscles - moves the ribs down and in
thoracic volume - decreases
thoracic pressure - increases
air flow - OUT of the lungs
